Steel-making



United States Patent STEEL-MAKING Ernest S. Starkman, El Cerrito, Calif,and Stanley S. Sorem, Brombrough, Wirral, England, assignors to ShellDevelopment Company, San Francisco, Calif, a corporation of Delaware N0Drawing. Application June 24, 1950, Serial No. 170,249

3 Claims. (Cl. 75-43) This invention relates to the production of steel,particularly by the open hearth processes, and to fuels for use in suchprocesses.

One of the most frequent reasons for interrupting open hearth furnaceoperations is the necessity for cleaning out the regenerative heatingchambers, known as checker chambers, so that such may function properly.The cleaning consists primarily of removing slag, dirt, soot or carbondeposits, etc., the amounts and types of these deposits dependinglargely upon the type of fuel used. When liquid hydrocarbon fuels, suchas residual fuel oils, are burned, there are large quantities of sootand carbon deposited in said chambers.

It has been known for some time that carbon and soot resulting from theburning of liquid hydrocarbon fuels could be eliminated, orsubstantially reduced, by incorporating relatively small amounts of basemetal compounds, such as, for example, sodium or calcium naphthenates,into the fuel. However, in situations where the fuels were being burnedin furnaces containing acidic refractories, such as the silica brick inopen hearth furnaces, it has not been possible to use these base metalsbecause of their deleterious effects upon the acidic refractories.

Another problem which has recently arisen in the steelmaking industry isa result of the increasingly high sulfur content of residual, or bunker,fuel oils. When these high sulfur content fuels are used, it has beenfound that the time required to complete a heat is increased by as muchas ten or twenty percent because of difficulty in reducing the sulfurcontent of the metallic charge to required specifications. In order toavoid this latter difi'iculty, it has been necessary to include amaximum sulfur concentration limitation in the specifications for suchfuels, the general result of which has been to make such fuels moreexpensive-an obviously undesirable result.

It has now been found that the combined presence of base metal compoundsand sulfur will substantially eliminate the deleterious effects of bothof such substances. More particularly, it has been found that the use ofsuch materials in open hearth furnaces will not adversely afiect theacidic refractories, and, at the same time, will not increase the timerequired to reduce the sulfur content of the steel to the desiredconcentration.

The term base metal, or alkaline metal, as used herein, is meant toembrace only alkali metals and alkaline earth metals, such as sodium,potassium, cesium, calcium, magnesium, barium, etc. The alkali metals,and sodium in particular, are preferred for use according to thisinvention.

The base metal compound may be added at any point of the operation priorto that where the fuel combustion products contact the charge in thehearth, so long as the sulfur is also present at the time that such basemetal compounds are exposed to the heated acidic refractories. Thus, themetal compounds may be injected directly into the flame, may becontrollably injected into the fuel stream just prior to combustion, ormay be originally blended into the fuel as an integral componentthereof.

The particular type of base metal compound is not critical, and willusually depend upon the manner in which it is utilized. If it is to beblended into the fuel as a permanent component, it will usually beconvenient to use an oil-soluble form, such as the base metal salt of anaphthenic acid, of a sulfonic acid, of a phenol, or the like. However,inorganic forms may also be used, for example, by suspending the solidcompound in the oil or dissolving it by means of a suitable co-solvent.Thus, sodium hydroxide may be incorporated into the oil by firstdissolving in alcohol and then adding the alcohol solution to the fuel.Where an injection is made in the fuel stream or directly into thecombustion chamber, any fluid form may be used, such as oil, alcohol,acetone or Water solutions, etc. Even when injecting into the fuelstream it is not necessary that the injected fluid be soluble in theoil, especially if the fuel is in turbulent flow.

The sulfur which is required to overcome the deleterious effects of thesodium may be present in any form, for example, as mercaptans, sulfides,disulfides, as elemental sulfurs, etc. The most practical method ofobtaining the sulfur will generally be by securing unusually high sulfurcontent fuels; however, if it is desired to enjoy the benefits of thisinvention while burning low sulfur fuels, the sulfur may be added in anyform and in any manner, just as in the case of the base metal compoundaddition.

The relative quantities of sulfur and base metal are closely related andquite critical. In general, these amounts should be controlled by therelation:

wherein S and M are weight percent of sulfur and alkaline metal,respectively, based upon the quantity of fuel burned, A is the hydrogenequivalent of the alkaline metal, and m. w. is the molecular weight ofsaid metal. For best results, the last term of the above relationshipshould be limited to :025.

From this relationship it may be readily seen that when the sulfurcontent of the fuel is in the lower ranges of about 0.5% or below, thereis no need for the presence of the base metal in the furnace, andconsequently that there is no advantage to be derived from the presentinvention in such cases. In order to derive the benefits of thisinvention it is necessary to use at least about 0.05% of the metal, andpreferably more than about 0.1%, based upon the fuel consumption, and,of course, a commensurate amount of sulfur. On the other hand, not morethan about 2%, or at the most, 3%, of the alkaline metal may be usedbecause of the unduly high amounts of sulfur which would be required tocounteract the effect of greater quantities of metal. From the aboveequation it will be evident that for a base metal concentration range of0.1 to 1% by weight and in the case of the preferred base metal, sodium,the sulfur content of the finished fuel oil composition should be fromabout 0.8% to about 1.9% by weight for best results. The minimum sulfurcontent of the finished fuel oil in this case, 0.8%, is derived bysubstituting a base metal concentration of 0.1%, and the constants forsodium, into the above equation with the last term being 0.25. Thus,this minimum sulfur content The maximum sulfur content of the finishedfuel oil in this case, 1.9%, is derived by substituting a base metalconcentration of 1.0%, and the constants for sodium,

into the above equation with the last term being +0.25. Thus, thismaximum sulfur content While the present invention is primarily directedto the method of refining pig iron in an open hearth furnace, it will bereadily apparent that the fundamental concepts involved are applicableto many other operations, which are intended to be included within thescope of this application. Moreover, it is believed that the fuelcompositions formed when the present invention is practiced by addingthe base metal to a suitable sulfur content residual fuel are novelcompositions, and such are also contemplated as a part of the invention.

In confirming the advantages set forth hereinbefore, samples of silicarefractory brick were exposed to flames containing varying amounts ofsulfur and sodium. The results were as set forth in the table.

Table Weight percent, based on fuel Appearance of silica S Na 0.25 1.0Heavily glazed. 1. 1.0 Slightly glazed. 1. 0 0. 5 Substantiallyunchanged.

The invention claimed is:

1. A liquid residual fuel oil composition comprising a a predominantamount of a bunker fuel oil, more than 0.10% up to about 1% by weight ofsodium in the form of sodium naphthenate and between about 0.8% andabout 1.9% by Weight of sulfur, the weight percent of sulfur presentalso being equal to 0.7 M+0.99i0.25,

wherein M is equal to the weight percent of sodium present.

2. A liquid residual fuel oil composition comprising a predominantamount of a bunker fuel oil and containing about 1.0% by weight ofsulfur and about 0.5% by weight of sodium in the form of sodiumnaphthenate.

3. In a process of reducing carbon and soot deposition on the surfacesof the regenerative heating chambers of an open hearth furnace providedwith an acidic refractory lining by the use of a residual fuel oilcontaining a compound of an alkali or alkaline earth metal, theimprovement comprising the reduction of the chemical attack on theacidic refractory material in said furnace by the combustion, as theonly fuel in said furnace, of a residual fuel oil containing about 1.0%by weight of sulfur and about 0.5% by Weight of sodium in the form ofsodium naphthenate.

References Cited in the file of this patent UNITED STATES PATENTS1,419,801 Basset June 13, 1922 2,045,788 Maverick June 30, 19362,141,848 Adams et a1 Dec. 27, 1938 2,167,345 Crandall et al. July 25,1939 2,205,126 Seeley et al June 18, 1940 2,230,642 Fischer et al. Feb.4, 1941 2,230,817 Shoemaker Feb. 4, 1941 2,360,584 Risk Oct. 17, 19442,361,054 Pevere Oct. 24, 1944 2,362,085 Morgan Nov. 7, 1944 2,460,700Lyons Feb. 1, 1949 FOREIGN PATENTS 12,401 Great Britain of 1888 496,692Great Britain Dec. 5, 1938

1. A LIQUID RESIDUAL FUEL OIL COMPOSITION COMPRISING A PREDOMINANTAMOUNT OF A BUNKER FUEL OIL, MORE THAN 0.10% UP TO ABOUT 1% BY WEIGHT OFSODIUM IN THE FORM OF SODIUM NAPHTHENATE AND BETWEEN ABOUT 0.8% ANDABOUT 1.9% BY WEIGHT OF SULFUR, THE WEIGHT PERCENT OF SULFUR PRESENTALSO BEING EQUAL TO 0.7 M+0.99$0.25, WHEREIN M IS EQUAL TO THE WEIGHTPERCENT OF SODIUM PRESENT.